Search

A molecular imprinted electrochemical sensor based on boron-functionalized graphitic carbon nitride (B-g-C3N4) and graphene quantum dots (GQDs) was presented for selective determination of bisphenol A (BPA). In particular, by combining the selectivity and high stability properties, which are the most important advantages of molecular imprinted polymers, and the highly sensitive properties of GQDs/B-g-C3N4 nanocomposite, a highly selective and sensitive analytical method was developed for BPA analysis. Firstly, GQDs/B-g-C3N4 nanocomposite was characterized by using microscopic, spectroscopic, and electrochemical techniques. This novel molecular imprinted electrochemical sensor for BPA detection demonstrated a linearity of 1.0 × 10−11–1.0 × 10−9 M and a low detection limit (LOD, 3.0 × 10−12 M). BPA-imprinted polymer on GQDs/B-g-C3N4 nanocomposite also showed good stability, repeatability and selectivity in food samples. [ABSTRACT FROM AUTHOR]

Herein, electrochemical tau protein immunosensor based on manganese sulfide nanoparticles/graphene oxide/polyaniline (MnS/GO/PANI) and magnetite‐incorporated gold nanoparticles (AuNPs@Fe3O4) was constructed. After the modification of the glassy carbon electrode (GCE) with MnS/GO/PANI, the immobilization and conjugation of anti‐Tau capture antibody and antigen Tau protein were successfully completed on MnS/GO/PANI/GCE, respectively. Then, the conjugation of anti‐Tau secondary antibody was carried out to AuNPs@Fe3O4 as signal amplification via amino‐gold affinity and the eventual immunosensor was accomplished by the distinctive interactions of electrode platform and signal amplification. Final immunosensor demonstrated the quantification limit (LOQ) of 1.0×10−13 M and the detection limit (LOD) of 1.0×10−14 M. [ABSTRACT FROM AUTHOR]

Serotonin (SER) is the important neurotransmitter and its amount in human body can affect the human life. The low level results in anxiety and carcinoid syndrome. Its high level causes crucial toxicity. Molecularly imprinted approach was used in designing a new electrochemical sensor for serotonin (SER) detection in urine samples. The sensor was prepared based on graphene quantum dots (GQDs) incorporated two-dimensional (2D) hexagonal boron nitride (2D-hBN) nanosheets. All nanomaterials’ formation and properties were highlighted with scanning electron microscope (SEM), transmission electron microscope (TEM), X-ray photoelectron spectroscopy (XPS), X-ray diffraction (XRD) method, cyclic voltammetry (CV) and electrochemical impedance spectroscopy (EIS). SER imprinted voltammetric sensor was improved in presence of 80.0 mM phenol containing 20.0 mM SER by CV. 1.0 × 10 −12 –1.0 × 10 −8  M and 2.0 × 10 −13  M were founded as the linearity range and the detection limit (LOD). SER imprinted glassy carbon electrode (GCE) was used for urine sample analysis in presence of the other competitor agents such as dopamine (DOP), tryptophan (TRY) and norepinephrine (NOR). The sensor was also investigated for stability and selectivity. [ABSTRACT FROM AUTHOR]

In this report, ruthenium nanoparticles (RuNPs) and calix[4]amidocrown-5 (C4A5) were synthesized and grafted onto the surface of reduced graphene oxide (RGO) nanocomposite (RuNPs/C4A5/RGO). The morphologies of the nanocomposites were characterized by transmission electron microscope, scanning electron microscope, atomic force microscope, electrochemical impedance spectroscopy and x-ray photoelectron spectroscopy. The electrochemical experiments were performed by cyclic voltammetry, electrochemical impedance spectroscopy and square wave voltammetry. The simultaneous determination of quercetin, rutin and morin was performed on glassy carbon electrode modified with RuNPs/C4A5/RGO (RuNPs/C4A5/RGO/GCE). The linearity ranges and the detection limits of QR, RT and MR were 1.0×10−10-1.0×10−8 M and 2.0×10−11 M respectively. [ABSTRACT FROM AUTHOR]

The catalysts based on 2-aminoethanethiol functionalized graphene oxide (AETGO) with several mono-metallic and bi-metallic nanoparticles such as rod gold (rAuNPs), rod silver (rAgNPs), rod gold-platinum (rAu-Pt NPs) and rod silver-platinum (rAg-Pt NPs) were synthesized. The successful synthesis of nanomaterials was confirmed by various methods. The effective surface area (ESA) of the rAu-Pt NPs/AETGO is 1.44, 1.64 and 2.40 times higher than those of rAg-Pt NPs/AETGO, rAuNPs/AETGO and rAgNPs/AETGO, respectively, under the same amount of Pt. The rAu-Pt NPs/AETGO exhibited a higher peak current for methanol oxidation than those of comparable rAg-Pt NPs/AETGO under the same amount of Pt loading. [ABSTRACT FROM AUTHOR]

In this study, we report the synthesis of rod shaped gold nanoparticles/2-aminoethanethiol functionalized reduced graphene oxide composite (rdAuNPs/AETrGO) and its application as an anode material for lithium-ion batteries. The structure of the rdAuNPs/AETrGO composite was characterized by scanning electron microscopy, transmission electron microscopy, X-ray photoelectron spectroscopy and X-ray diffraction. The electrochemical performance was investigated at different current rates by using a coin-type cell. It was found that the rod shaped gold nanoparticles were highly dispersed on the reduced graphene oxide sheets. Moreover, the rdAuNPs/AETrGO composite showed a high specific gravimetric capacity of about 1320 mAh g − 1 and a long-term cycle stability. [ABSTRACT FROM AUTHOR]

Abstract: In this study, a novel catalyst based on Fe@Au bimetallic nanoparticles involved graphene oxide was prepared and characterized by transmission electron microscope (TEM), and x-ray photoelectron spectroscopy (XPS). The nanomaterial was used in catalytic reductions of 4-nitrophenol and 2-nitrophenol in the presence of sodium borohydride. The experimental parameters such as temperature, the dosage of catalyst and the concentration of sodium borohydride were studied. The rates of catalytic reduction of the nitrophenol compounds have been found as the sequence: 4-nitrophenol>2-nitrophenol. The kinetic and thermodynamic parameters of nitrophenol compounds were determined. Activation energies were found as 2.33 kcal mol−1 and 3.16 kcal mol−1 for 4-nitrophenol and 2-nitrophenol, respectively. The nanomaterial was separated from the product by using a magnet and recycled after the reduction of nitrophenol compounds. The recyclable of the nanocatalyst is economically significant in industry. [Copyright &y& Elsevier]

Highlights: [•] We prepared mercaptophenyl boronic acid terminated Ag@AuNPs/graphene oxide. [•] The prepared nanocomposites were characterized by using various techniques. [•] The nanocomposite shows excellent SERS activity. [•] The biosensor was applied for the determination of glucose in blood samples. [ABSTRACT FROM AUTHOR]

Highlights: [•] We prepared glassy carbon electrode modified with AuNPs–modified graphene oxide. [•] The prepared composites were characterized by using various techniques. [•] The validated method was applied for determination of quercetin in pharmaceuticals. [Copyright &y& Elsevier]

Chlorpyrifos is widely used to control pest insects in residential, agricultural, and commercial applications. Its common use has led to the release of chlorpyrifos into sediments, wastewater and water sources. The presence of chlorpyrifos in wastewaters and water sources may affect ecosystem and human health due to its chronicle toxicity to aquatic organisms. In this study, magnetic recoverable CoFe 2 O 4 @TiO 2 decorated reduced graphene oxide nanocomposite was prepared and used for investigating the photodegradation of chlorpyrifos. The nanocomposite was characterized by using transmission electron microscopy, X-ray photoelectron spectroscopy, X-ray diffraction and scanning electron microscopy. In photocatalytic degradation of chlorpyrifos experiments, the effect of operating variables such as initial chlorpyrifos concentration, catalyst dosage and contact time was also investigated. The photocatalytic degradation of chlorpyrifos followed the pseudo-first-order kinetic model. The results indicated that the nanocomposite exhibited a high efficient photocatalytic activity on the photodegradation of chlorpyrifos. The nanocomposite was separated from the solution by a magnet and reused after the photodegradation of chlorpyrifos. The recyclable of the nanocomposite is economically significant in the industry. [ABSTRACT FROM AUTHOR]

In present study, a sensitive imprinted electrochemical sensor based on cubic gold nanoparticles (cAuNPs) involved in 2-aminoethanethiol (2-AET) functionalized graphene oxide (GO) modified glassy carbon (GC) electrode was developed for determination of tyrosine (Tyr). The prepared nanomaterials were characterized by using scanning electron microscope (SEM), transmission electron microscope (TEM), X-ray photoelectron spectroscopy (XPS) and reflection–absorption infrared spectroscopy (RAIRS). Tyr imprinted film was constructed by cyclic voltammetry (CV) for 20 cycles in the presence of 80 mM phenol in phosphate buffer solution (pH 7.0) containing 20 mM Tyr. The imprinted electrochemical sensor was validated according to the ICH guideline and found to be linear, sensitive, precise and accurate. The linearity range and the detection limit were obtained as 1.0 × 10 −9 to 2.0 × 10 −8 M and 1.5 × 10 −10 M, respectively. The developed imprinted sensor was successfully applied to milk samples. In addition, the stability and reproducibility of the prepared molecular imprinted electrode were investigated. The excellent long-term stability and reproducibility of the prepared Tyr imprinted electrodes make them attractive in electrochemical sensors. [ABSTRACT FROM AUTHOR]

A novel and sensitive electrochemical biosensor for selective determination of DNA was developed based on Fe@Au nanoparticles (Fe@AuNPs) involving 2-aminoethanethiol (AET) functionalized graphene oxide (GO) (Fe@AuNPs-AETGO). Firstly, 5′-TA CCG GGT GCT CGA GCT-(CH2)3-SH-3′ single-stranded probe (ss-DNA) was immobilized on Fe@AuNPs-AETGO nanocomposite to form ssDNA-Fe@AuNPs-AETGO. Square wave voltammetry (SWV) was applied to monitor the DNA hybridization by basic blue 41 (BB41) as an electrochemical indicator. The DNA immobilization and hybridization on the film were studied by cyclic voltammetry (CV), SWV and electrochemical impedance spectroscopy (EIS). Under optimum conditions, the peak currents of BB41 were linear with the logarithm of the concentrations of complementary DNA (5′-AT GGC CCA CGA GCT CGA-(CH2)3-SH-3) from 1.0×10−14 to 1.0×10−8 M with a detection limit of 2.0×10−15 M. The biosensor also showed high selectivity to one-base, two-base and three-base mismatched DNA. Compared with the other electrochemical DNA biosensors, the proposed biosensor showed its own performance of simplicity, good stability and high sensitivity. [ABSTRACT FROM AUTHOR]

Abstract: A fuel cell is an electrochemical cell that converts a source fuel into an electrical current. It generates electricity inside a cell through reactions between a fuel and an oxidant, triggered in the presence of an electrolyte. Fuel cells have been attracting more and more attention in recent decades due to high-energy demands, fossil fuel depletions, and environmental pollution throughout world. In this study, different sized metallic and bimetallic nanoparticles (AuNPs, Fe@AuNPs, Ag@AuNPs) were synthesized on graphene oxide sheets and their electrocatalytic activities for methanol oxidation were investigated. All the catalysts were characterized by transmission electron microscope (TEM) and X-ray photoelectron spectroscopy (XPS). Electrochemical measurements are performed to compare the catalytic efficiencies of methanol oxidation. Experimental results demonstrated that graphene oxide-supported bimetallic nanoparticles enhanced electrochemical efficiency for methanol electro-oxidation with regard to diffusion efficiency, oxidation potential and forward oxidation peak current. Graphene oxide-supported Ag@AuNPs, in comparison to graphene oxide-supported Fe@AuNPs and AuNPs, showed the more efficiency for methanol electro-oxidation. [Copyright &y& Elsevier]

Highlights: [•] We electrochemically prepared sensor based on graphene oxide. [•] The prepared electrode was characterized by using various techniques. [•] The proposed nanosensor showed good stability, selectivity and high sensitivity. [•] The proposed nanosensor electrode was used for the analysis of Cd(II) and Cu(II). [ABSTRACT FROM AUTHOR]

A glassy carbon electrode (GCE) modified by calixarene functionalized reduced graphene oxide (CA/RGO) has been fabricated and utilized in this study for simultaneous voltammetric detection of several metal ions, Fe(II), Cd(II) and Pb(II), in aqueous solution. The CA/RGO nanocomposite was characterized in surface and electrochemical properties using scanning electron microscopy (SEM), infrared spectroscopy (IR), X-ray photoelectron spectroscopy (XPS), atomic force microscopy (AFM), Raman spectroscopy and electrochemical impedance spectroscopy (EIS). The CA/RGO coating significantly improves the sensitivity of electrochemical responses and separation of heavy metals. The electrochemical oxidation of Fe(III), Cd(II), and Pb(II) was performed by square wave voltammetry (SWV). The metal ions, Fe(III), Cd(II), and Pb(II), gave a linear relationship with their concentrations at 1.0 × 10 −10 – 1.0 × 10 −8 M on the CA/RGO/GCE. The detection limits of the metal ions were found to be similar at 2.0 × 10 −11 M. A good recovery was also obtained for practical use of the CA/RGO/GCE in pharmaceutical formulation. [ABSTRACT FROM AUTHOR]

In this report, a novel voltammetric sensor based on polyoxometalate (H 3 PW 12 O 40 , POM) functionalized reduced graphene oxide (rGO) modified glassy carbon electrode (GCE) was presented for simultaneous determination of l -tyrosine ( l -Tyr) and l -tryptophan ( l -Trp). The nanocomposites were characterized by transmission electron microscopy (TEM), X-ray photoelectron spectroscopy (XPS), X-ray diffraction (XRD), electrochemical impedance spectroscopy (EIS) and cyclic voltammetry (CV). The electrochemical determination of l -Tyr and l -Trp has been studied using square wave voltammetry (SWV) on GCE modified with POM-rGO composite (POM-rGO/GCE). The developed method was also applied successfully for the simultaneous determination of l -Tyr and l -Trp in spiked serum sample and the linearity range of l -Tyr and l -Trp was 1.0 × 10 −11 − 1.0 × 10 −9 M with the detection limit of 2.0 × 10 −12 M. [ABSTRACT FROM AUTHOR]

In this study, the removal and recovery of hexavalent chromium using reduced graphene oxide based polymer inclusion membrane from chrome plating water was investigated. The prepared modified membrane improved the mechanical properties and permeability of polymer inclusion membrane. Important outcomes of this study are high permeability, seamless porous structure, high selectivity and development of the polymer inclusion membrane by minimized nano-reinforced against pollution in addition of the unique physical properties of graphene oxide. The effects of carrier concentration, plasticizer type and temperature on the transport, the membrane's stability and thickness were examined. The polymer inclusion membrane was characterized by using atomic force microscopy, X-photo electron spectroscopy and contact angle measurements. The transport efficiency of Cr(VI) from chrome plating bath water was found to be 100% under optimized conditions. The experimental results showed that reduced graphene oxide modified polymer inclusion membrane exhibits great stability and selectivity in the presence of other metal cations in chrome plating bath water for the removal of Cr(VI). [ABSTRACT FROM AUTHOR]

In this report, silver nanoparticles (AgNPs) with the mean diameters of 10-30nm were self-assembled onto the surfaces of 2-aminoethanethiol (2-AET) functionalized graphene oxide (AETGO) sheets. The graphene oxide (GO) and AgNPs-AETGO nanocomposites were characterized by a transmission electron microscope (TEM), x-ray photoelectron spectroscopy (XPS), reflection–absorption infrared spectroscopy (RAIRS) and the x-ray diffraction (XRD). The simultaneous determination of quercetin (QR) and morin (MR) has been performed on glassy carbon electrode (GCE) modified with AgNPs-AETGO (AgNPs-AETGO/GCE). QR presented an oxidation step at Ea of 200mV and reduction step at Ec of 150mV and RT presented an oxidation step at Ea of 600mV at AgNPs-AETGO/GCE by cyclic voltammetry (CV). The linearity ranges and the detection limits of QR and MR were 1.0×10-8 - 5.0×10-6M and 3.3×10-9M, respectively. The AgNPs-AETGO/GCE was also applied to real samples for the simultaneous determination of QR and MR. Thus the developed method can be adopted as an alternative to the published chromatographic, spectrophotometric and electroanalytical methods for simultaneous determination of QR and MR. [ABSTRACT FROM AUTHOR]

A highly sensitive method for detection of DNA hybridization was developed. This method was based on the modification of glassy carbon electrode with gold nanoparticles (AuNPs) involving p-aminothiophenol (ATP) functionalized graphene oxide (GO). This GO was used as a platform for impedimetric genosensing using 5′-TA GGG CCA CTT GGA CCT-(CH2)3-SH-3′ single-stranded probe (ss-DNA), 5′-AGG TCC AAG TGG CCC TA-3′ (target DNA), 5′-SH-C6-TAG GGC CA-3′ (non-complementary-1) and 5′-SH-C6-TGC CCG TTA CG 3-′ (non-complementary-2) oligonucleotide sequences. The film exhibited excellent properties for immobilizing DNA probes and sensing DNA hybridization. The DNA immobilization and hybridization on the film were studied by cyclic voltammetry (CV), and electrochemical impedance spectroscopy (EIS), and found that the charge transfer resistance (R ct) of the electrode increased with the concentration of the target DNA hybridized with the ss-DNA. The linear detection range was from 1.0×10−13 M to 1.0×10−7 M and the detection limit was 1.10×10−14 M (n =6). Compared with the other electrochemical DNA biosensors, the proposed biosensor showed its own performance of simplicity, good stability, and high sensitivity. [ABSTRACT FROM AUTHOR]